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Topic: Voice coil

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	Coil Encyclopedia Articles @ HotAndCold.com (Hot and Cold) (Site not responding. Last check: 2007-10-24)
		A Oudin coil is a disruptive discharge coil.
		A chemistry coil is a tube of spiral form, used commonly to cool originating steam of the distillation and thus to condense them in liquid form.
		The RNA coil is a nucleic acid structure consisting of a string of covalently-bound nucleotides.
	www.hotandcold.com /encyclopedia/Coil (953 words)

	Heat dissipating device for loudspeaker voice coil - Patent 3991286
		Voice coil 12 operates in conventional fashion in the gap between the pole pieces formed by magnetic members 11 and 13 to cause mechanical actuation of the coil, coil form and cone in accordance with the electrical signals fed to the coil.
		Voice coil 12 is wound around coil form 14 which is fabricated of a highly thermally conductive material such as aluminum or copper.
		Voice coil 12 is supported in the magnetic gap formed between circularly shaped magnetic pole plate element 30 and phasing plug 28 which also forms a pole piece.
	www.freepatentsonline.com /3991286.html (1683 words)

	The Voice Coil and Magnet
		The voice coil assembly is suspended by the centering device in the air gap (Fig.
		The voice coil magnetic field direction is alternately reversed and aligned by the amplifier signal to the unchanging direction of the magnetic field in the air gap (Figs.
		Thus, the voice coil assembly is attracted and then repelled by the field of the magnet, which forces both the assembly and the attached loudspeaker cone to move backward and forward.
	www.cyberus.ca /~ec091357/TheVoiceCoilAndMagnet.shtml (594 words)

	JL Audio: W7 Voice Coil
		The W7 voice coils are huge and by far the largest JL Audio has ever made (in diameter and winding height).
		The 8W7 uses a 2.25-inch diameter coil (2.0-inch winding height), the 10W7 uses a 2.75-inch diameter coil (2.3-inch winding height), the 12W7 employs a 3-inch unit (2.8-inch winding height) and the 13W7 enters battle with a 3.55-inch diameter voice coil (3.0-inch winding height).
		Since the W7 is an extreme excursion speaker with a detachable surround, voice coil former resilience is a key parameter.
	mobile.jlaudio.com /products_subs_pages.php?page_id=45 (933 words)

	Fall 1998 MOTION Magazine - Voice Coil Actuators (Site not responding. Last check: 2007-10-24)
		When current is applied to the circumferentially-wound coil, it interacts with the radial magnetic field of the permanent magnet assembly via the Lorentz Force Principle to create an axial force (i.e., mutually perpendicular to the vectors of the current flow and the magnetic field) between the coil and magnet assemblies.
		Voice coil actuators are usually sold as a parts set consisting of a magnet assembly and a coil assembly.
		Other voice coil applications requiring high frequency operation include linear cryocoolers, refrigerators, and various other pumps, where the actuators are operated in resonance against a gas spring to provide the necessary compression for the particular cooling cycle employed.
	www.motion.org /9804morc.htm (1759 words)

	MachineDesign.com: Where do voice-coil actuators fit in? (Site not responding. Last check: 2007-10-24)
		This linear voice coil actuator (BEI Kimco 's LA16-27-000A) is housed with its own bearings and can be used as a stand-alone component for such applications as valve control (pressure and flow), laser beam steering, auto-focus in optical applications and tension control in textile applications.
		When current flows through the coil, it generates an axial force on the coil and produces relative motion between the field assembly and coil, providing the force is enough to overcome friction, inertia, and other forces from loads attached to the coil.
		Although the principles of operation are analogous to that of linear voice coils, ratings for rotary voice coils are in units of torque instead of force, because force is generated along the circumference of an arc.
	www.machinedesign.com /ASP/strArticleID/56123/strSite/MDSite/viewSelectedArticle.asp (1009 words)

	b e a . s t - Voice Coil Actuator Array
		Care is taken so that the upper and lower sections of the voice coil lay outside the magnetic field, as they would cause extraneous forces on the system upward and downward, which would increase friction and therefore degrade performance.
		By press-fitting the dowel pin into the nylon voice coil section and rotating it in the sleeve bearings, instead of pressing it into the plates and rotating it at the location of the voice coil, any misalignment, imperfection or over sizing of bearing surface will minimize angular error of the voice coil.
		The output of the full bridge is the voice coil, which provides a high enough impedance that it does not require any power resistors in series (or PWM limiting) to current limit it.
	bea.st /sight/array (793 words)

	Body
		The coil internal thermal resistance will probably be found to be insignificant compared with the thermal resistance of the boundary layer of air at the surface of the coil.
		When a steady DC current is passed through the coil, a magnetic field is set up which adds to or reduces the static field (depending on the directions of current and field) increasing or decreasing the degree of saturation of the center pole steel.
		As generally applied today, it means a coil of wire with an outer flux return path of permeable material (usually steel), with one end open and the other usually closed, and a magnetically permeable plunger which is pulled into the center of the coil when electric current is passed through the winding.
	www.consult-g2.com /course/chapter11/chapter.html (8084 words)

	diyAudio Forums - Voice coil and formers[bobbins] (Site not responding. Last check: 2007-10-24)
		Overhung- the voice coil extends past the polepiece in both directions, gives greater efficiency and linearity with larger excursions, but has a greater coil mass and therefore often a lower Frequency response.
		I have seen dual voice coil drivers with both the coils wound parallel, and one on top of the other, but I suspect parallel will give a better result, as the motor influence will be more symetrical between channels.
		The only real difference is in wether the voice coil is conductive or not, conductive voice coils tend to have a slightly rolled off high frequency response, but you would see this from the published or measured response anyway.
	www.diyaudio.com /forums/showthread.php?postid=84925 (444 words)

	Tutorial on the Rotary or Swing Arm Voice Coil Actuator used on modern Hard Disk (Site not responding. Last check: 2007-10-24)
		A Voice Coil Actuator is a very simple positioning device that utilizes a coil of wire in a permanent magnetic field.
		It is a 'voice coil actuator' in that it only uses a coil and a permanent magnet in a simple push-pull fashion, but doesn't work like a speaker voice coil actuator.
		The voice coil actuator in the disk generally has no 'natural position' that it springs to as is the case with speaker voice coil actuators.
	yuan.ecom.cmu.edu /rotaryvoicecoil (689 words)

	diyAudio Forums - Voice coil former generates motional feedback voltage?
		The voice coil former on higher powered speakers is often a strip of aluminium shim wrapped into a tubular shape with the ends not quite meeting so they don't form a shorted turn.
		This is in fact a ready made 1 turn coil that if you were very careful you could attach a pair of flexible wires to and voila you now have a feedback signal from it's own dedicated coil.
		A copper voice coil former would be better thermally and easy to solder too, so that would be a good choice if you got a driver made up special.
	www.diyaudio.com /forums/showthread.php?postid=73117 (812 words)

	[No title]
		I have always taken it on faith that the back EMF of a driver coil is equal to Blv, where v is the velocity of the voice* coil, and Bl is that mysterious driver spec.
		We will assume that the magnetic field (B) in the gap is uniform, and that the windings on the voice coil are evenly spaced and tightly packed (n).
		Let the north poles be outside the voice coil, and the south inside.
	www.arcavia.com /kyle/Equations/Coil.html (865 words)

	Voice Coil Actuators by Servo Magnetics Incorporated (Site not responding. Last check: 2007-10-24)
		Voice coil actuators are single-phase, two wire non-commutated direct-drive, hysteresis-free, cog-free devices used for providing highly accurate linear motion.
		They are limited-motion devices that use a permanent-magnetic field and coil to produce a force proportional to the current applied to the coil.
		Linear voice coil actuators were originally used in loudspeakers but they can now be found in linear and rotary-motion devices requiring linear force or torque and high acceleration (50 g or more) or high-frequency actuation (20 to 400 Hz).
	www.servomag.com /linear_actuators.html (484 words)

	Compact Moving Coil and Moving Magnet Voice Coil Linear Actuators Have No Cogging - H2W Technologies, Inc.
		Valencia, CA - An expanded series of non commutated, linear Voice Coil actuators has been introduced by H2W Technologies, Inc. Voice Coil or Moving Coil linear actuators from H2W Technologies, which are capable of producing in excess of 20 g's of acceleration, are available in stroke lengths from.05 in.
		Direct drive, Voice Coil, linear actuators feature low electrical and mechanical time constants and provide smooth, hysteresis-free motion over their entire speed range, including very low speeds.
		Voice Coil linear actuators are ideal for positioning applications such as laser beam steering mirrors, optical scanning, tracking, stabilizing, pointing and aiming, hermetically sealed cryo-cooler actuators, pumps, valve actuation, medical instruments and semiconductor manufacturing equipment.
	www.motionshop.com /pr/h2wact.shtml (426 words)

	Crutchfield Advisor - Subwoofers - Dual Voice Coil Subwoofers
		Dual voice coil subwoofers are becoming a popular choice among car audio enthusiasts who want more flexibility in wiring their sound systems.
		While typical subwoofers have a single voice coil, dual voice coil (DVC) subwoofers use two separate voice coils, each with its own connections, mounted on one cylinder, connected to a common cone.
		Parallel: A dual 4-ohm voice coil subwoofer with its coils wired in parallel presents a 2-ohm load to your amplifier.
	www.crutchfieldadvisor.com /learningcenter/car/subwoofers_dual.html (524 words)

	Bazooka Technical Forum - Dual Voice Coil question
		Well if you were talking about the speaker input on your sub, there's 2 speaker inputs on the sub because one if for each voice coil and it's easily possible to damage the sub if you only run one....
		Wiring voice coils in parallel is the same as wiring speakers in parallel.
		You want to make sure that the signal is identical for each voice coil, or they could end up fighting each other.
	www.sasbazooka.com /forum/topic.asp?TOPIC_ID=2267 (370 words)

	Voice Coil/Velocimeter (Site not responding. Last check: 2007-10-24)
		A basic electromagnet consisting of a wire wrapped coil and a magnet can be used to both drive the system (Voice Coil) measure the velocity of the system (Velocimeter).
		When the electromagnet is used to measure the velocity of the coils motion relative to the magnet, it is called a Velocimeter.
		When the coil moves relative to the magnetic field, a voltage is induced in the coil that is proportional to the relative velocity of the coil's motion within the magnetic field.
	bits.me.berkeley.edu /beam/vc_1.html (128 words)

	Stuffo "How Speakers Work" (Site not responding. Last check: 2007-10-24)
		In this way, the alternating current constantly reverses the magnetic forces between the voice coil and the permanent magnet.
		This changes the magnetic forces between the voice coil and the permanent magnet, moving the coil and attached diaphragm back and forth.
		The frequency and amplitude of this wave, which represents the original sound wave, dictates the rate and distance that the voice coil moves.
	www.stuffo.com /speaker6.htm (312 words)

	voice coil (Site not responding. Last check: 2007-10-24)
		If you are looking for voice coil actuators, then you have come to the right place.
		Voice coil actuators are dual wire, non-commutated, direct drive power, hysteresis free, and cog free devices used for providing highly accurate linear motion.
		Dual wire, high frequency, voice coil actuators deliver infinite position sensitivity, limited only by the encoder used for product feedback.
	www.servomag.com /voice_coil.html (90 words)

	Howstuffworks "How Speakers Work"
		When the electrical current flowing through the voice coil changes direction, the coil's polar orientation reverses.
		If you've read How Electromagnets Work, then you know that an electromagnet is a coil of wire, usually wrapped around a piece of magnetic metal, such as iron.
		Running electrical current through the wire creates a magnetic field around the coil, magnetizing the metal it is wrapped around.
	electronics.howstuffworks.com /speaker5.htm (289 words)

	Raw Drivers Features
		The spider is where the diaphragm/cone meets the voice coil.
		This process may or may not be linear and typically is related to the lossiness in the material.) One colleague whom I respect greatly feels that the joint between the voice-coil former and the cone may be to blame.
		The profile of the cone and distribution of material, the properties of the surround and spider at various frequencies, the voice coil geometry and materials, the magnetic structure, etc. all play a large role in the final performance of the driver.
	rockfordfosgate.com /ezcompare/ExternalFiles/RawDriverFeatures.asp?... (2410 words)

	H-O-Alternators.com - High Output Alternators for Automobiles
		Dual Voice Coil (DVC) woofers are simply speakers with two voice coils wrapped around the same voice coil former.
		With the individual coils wired in series, the resulting impedance will be 2 times the impedance of each individual coil.
		This means that a speaker with dual 4 ohm coils can be wired to 2 ohms or 8 ohms.
	www.highoutputalternator.com /TechCalcs/DVCSubinfo.htm (85 words)

	Voice Coil Actuator produces 9.5 lb of continuous force., Servo Magnetics, Inc.
		Voice Coil Actuator produces 9.5 lb of continuous force., Servo Magnetics, Inc.
		Voice Coil Actuator produces 9.5 lb of continuous force.
		Servo Magnetics Inc. - Canoga Park, CA; A new compact linear voice coil actuator from Servo Magnetics Inc. is well suited for applications that require a linear force with high acceleration, or high frequency actuation.
	news.thomasnet.com /fullstory/456526 (813 words)

	Voice Coil Theory of Operation (Site not responding. Last check: 2007-10-24)
		F is the force generated in the coil,
		N is the number of turns of the coil,
		L is the length of the coil exposed to the magnetic field, and
	bits.me.berkeley.edu /beam/vc_2.html (142 words)

	Car Audio : dual voice coil?
		So basically what i want to know is: does "dual voice coil" mean that there are just 2 different terminals to the single voice coil for wiring flexibility or are there 2 independent voice coils that have a power terminal for each?
		Some brands give power ratings "per voice coil" and others give ratings "with both voice coils wired." If it's "per," then the listed rating would be fine into one VC.
		Before I knew much about audio and wiring I put a dual voice coil sub into a powered home sub whos amp only put single 4 ohm, and i guess that's why it sounded so crappy.
	www.the12volt.com /installbay/forum_posts.asp?TID=52398&PN=1 (649 words)

	Free information on Boomboxes 12 dual voice coil subwoofer . Actual user testimonials and many links.
		12' Dual Voice Coil Subwoofers with 200 Watts RMS
		Voice coil is wound on a high-temperature former to promote (jk clothing)high power handling, double row of stitching binds the cone to the surround fortifying the structural integrity of (h h clothes)the woofer
		Rockford Fosgate P312D4 Punch Stage 3 12' subwoofer with dual 4-ohm voice coils
	boomboxes.canteachsw.org /12-dual-voice-coil-subwoofer.htm (356 words)

	Why dual voice coil subs? - FULLSIZEforums - Chevy Truck
		These are woofers with two separate voice coils mounted on a cylinder connected to a common cone.
		For this reason, dual voice coil woofers were developed so that a subwoofer or center speaker could be driven from the left and right channels of the average stereo home amp/receiver.
		Since sub-bass frequencies are hard to localize, the dual voice coil subwoofer allowed sub-bass reinforcement within one cabinet and one speaker.
	www.fullsizechevy.com /forums/showthread.php?t=41834 (659 words)

	Audio Talk! - Question about Dual Voice Coil Subwoofer
		Each of the coils on the Cerwin Vega are 4 ohms.
		and the voice coils would be driven in tandem.
		voice coil of a dual voice coil subwoofer?
	www.allaudio.org /detail-1869540.html (1000 words)

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